A massive, cigar-shaped craft silently hovers in the night sky above the GM Desert Proving Grounds in Mesa, Arizona. As rattlesnakes slither for cover in the moonlight and wolves howl, the alien vessel settles onto the blacktop several miles behind the highly secure front gate.

A large rectangular door opens in the belly of the craft and several occupants dressed in white lab coats emerge into the darkness. They form a line and begin gesturing with deliberate hand signals for the unloading process to begin.

One by one they roll a series of mysterious fiberglass machines out into the cool desert air. Arranged in a grid, they are unlike any others. Their work completed, the visitors re-board the craft and just as quickly as it appeared, it glides upward and through the cloud cover. Never to be seen again.

While there is no proof they came from another planet, Chevrolet brought an otherworldly stash of Corvettes from the GM Heritage Collection to the recent Barrett-Jackson collector car auction in Scottsdale, AZ. In addition to the mystery Corvettes, nearly 240 cars from virtually every division-–from GMC to Saturn-- were brought to the altar.

Though many of the offerings were former SEMA show vehicles, production milestone vehicles and restored vintage muscle and classic cars previously used for promotional purposes, the stash of rarely seen Corvette engineering prototypes and mule cars offer begs the UFO comparison.

You see, factory built experimental cars fall into two categories: those that are intended to be shown to the public and those that are not. When it comes to the second niche, you have to remember that every single car on the road today was once a top secret project-–with plenty of dead ends and redesigns before the first production-ready example rolled off the assembly line and onto the showroom floor.